When the Cold War-era Space Race started in the 1950s, no one really thought about the future trash problem. But now there are more than 21,000 pieces of orbital debris in Earth's orbit, including a growing cluster in geosynchronous orbit where a lot of valuable satellites are, as well as near the International Space Station in low-Earth orbit.

In 2009, there was an accidental collision that took out a communications satellite and the situation is only getting worse. There's even an Inter-Agency Space Debris Coordination Committee, with active participation from a number of nations' space programs including the U.S., India, Germany, Russia, Korea, and China.

Dr. Aaron Parness, Group Leader of Robotics at NASA's Jet Propulsion Laboratory, has a solution. His team built an anchoring system that cleans up the discarded rocket bodies and non-operational satellites. The interesting part? It's modeled on a gecko (yes, the animal with sticky feet).

Parness started this research when he arrived at Stanford for graduate school. "Originally we were thinking about wall-climbing robots, so I was interested in giving them more advanced mobility," Parness told PCMag. "That's when I turned to the natural world for inspiration. Geckos are the world's best climbers; they can hang their entire body weight from one toe. And the way they're able to do this is using this amazing microstructure that's on their feet: lots of tiny little hairs."

"So I started to do research on creating synthetic versions of these hairs and applying them to our robots to enable vertical climbing," he continued. "When I got to JPL, I started to think about microgravity [and] zero gravity, which is much more of a climbing problem than a walking problem. If you don't hang onto the surface you fall off—you float away into outer space."

These synthetic hairs, or "stalks," are a simplified version of those on a real-life gecko's foot; wedge-shaped with a slanted, mushroom-shaped cap (pictured above). When the gripping pad lightly touches part of an object, only the very tips of the hairs make contact with that surface. The stickiness turns on and off, depending on the direction of the hairs at any one time.

The temporary adhesiveness is explained by Van der Waals Forces (named for Nobel Prize-winning physicist Johannes Diderik van der Waals), where electrons orbiting the nuclei of atoms are not evenly spaced, creating a slight electrical charge and generating the force. Force is applied, increasing the area of contact between the "stalks" and surface, providing greater adhesion. When the force is relaxed, the "stalks" ping back to an upright position, and the stickiness is turned off.

The gripper is going to be most useful when attached to robot units as end effectors (hands) to participate in human/robot collaboration teams in space.

"Astronauts have a lot of constraints in the environment they're working in," explained Parness. "They have pressurized gloves, for instance, so their dexterity isn't what it could be. So getting robots to help them be effective is paramount. Our gripper technology could be used by a crawling robot moving along the outside of the International Space Station to do routine inspections, cleaning tasks, [and] checking equipment, so the human doesn't have to suit up and go out there until the robot finds a serious problem."

It all works beautifully in zero gravity. The grippers have been successfully tested at JPL on over 30 common materials used on spacecraft, and have also been tested inside a thermal vacuum chamber at temperatures of minus 76 degrees Fahrenheit to simulate the conditions of space. They also went up in a test flight through the Flight Opportunities Program of NASA's Space Technology Mission Directorate.

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"We tested in NASA's microgravity plane and nobody threw up, which was a relief, because it has a reputation for giving humans motion sickness," Parness quipped. "We demoed the grippers in several mission scenarios, like collecting debris and on a robot inspecting a satellite for maintenance. We had a floating cube that was 10kg with different textured surfaces commonly used on spacecraft and we were able to grab it, manipulate it, and release it just as you might grab a piece of debris, tow it down, and release it to burn up upon entering Earth's atmosphere. The hardest part was getting the floating debris and the operator to be in the same place at the same time, in that case a robot is better than a human."

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